1// Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15#include <assert.h>
16
17#include <openssl/bytestring.h>
18#include <openssl/digest.h>
19#include <openssl/hkdf.h>
20#include <openssl/hmac.h>
21#include <openssl/mem.h>
22
23#include "internal.h"
24#include "../../internal.h"
25#include "../service_indicator/internal.h"
26
27
28// tls1_P_hash computes the TLS P_<hash> function as described in RFC 5246,
29// section 5. It XORs |out_len| bytes to |out|, using |md| as the hash and
30// |secret| as the secret. |label|, |seed1|, and |seed2| are concatenated to
31// form the seed parameter. It returns true on success and false on failure.
32static int tls1_P_hash(uint8_t *out, size_t out_len,
33                       const EVP_MD *md,
34                       const uint8_t *secret, size_t secret_len,
35                       const char *label, size_t label_len,
36                       const uint8_t *seed1, size_t seed1_len,
37                       const uint8_t *seed2, size_t seed2_len) {
38  HMAC_CTX ctx, ctx_tmp, ctx_init;
39  uint8_t A1[EVP_MAX_MD_SIZE];
40  unsigned A1_len;
41  int ret = 0;
42
43  const size_t chunk = EVP_MD_size(md);
44  HMAC_CTX_init(&ctx);
45  HMAC_CTX_init(&ctx_tmp);
46  HMAC_CTX_init(&ctx_init);
47
48  if (!HMAC_Init_ex(&ctx_init, secret, secret_len, md, NULL) ||
49      !HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
50      !HMAC_Update(&ctx, (const uint8_t *) label, label_len) ||
51      !HMAC_Update(&ctx, seed1, seed1_len) ||
52      !HMAC_Update(&ctx, seed2, seed2_len) ||
53      !HMAC_Final(&ctx, A1, &A1_len)) {
54    goto err;
55  }
56
57  for (;;) {
58    unsigned len_u;
59    uint8_t hmac[EVP_MAX_MD_SIZE];
60    if (!HMAC_CTX_copy_ex(&ctx, &ctx_init) ||
61        !HMAC_Update(&ctx, A1, A1_len) ||
62        // Save a copy of |ctx| to compute the next A1 value below.
63        (out_len > chunk && !HMAC_CTX_copy_ex(&ctx_tmp, &ctx)) ||
64        !HMAC_Update(&ctx, (const uint8_t *) label, label_len) ||
65        !HMAC_Update(&ctx, seed1, seed1_len) ||
66        !HMAC_Update(&ctx, seed2, seed2_len) ||
67        !HMAC_Final(&ctx, hmac, &len_u)) {
68      goto err;
69    }
70    size_t len = len_u;
71    assert(len == chunk);
72
73    // XOR the result into |out|.
74    if (len > out_len) {
75      len = out_len;
76    }
77    for (size_t i = 0; i < len; i++) {
78      out[i] ^= hmac[i];
79    }
80    out += len;
81    out_len -= len;
82
83    if (out_len == 0) {
84      break;
85    }
86
87    // Calculate the next A1 value.
88    if (!HMAC_Final(&ctx_tmp, A1, &A1_len)) {
89      goto err;
90    }
91  }
92
93  ret = 1;
94
95err:
96  OPENSSL_cleanse(A1, sizeof(A1));
97  HMAC_CTX_cleanup(&ctx);
98  HMAC_CTX_cleanup(&ctx_tmp);
99  HMAC_CTX_cleanup(&ctx_init);
100  return ret;
101}
102
103int CRYPTO_tls1_prf(const EVP_MD *digest,
104                    uint8_t *out, size_t out_len,
105                    const uint8_t *secret, size_t secret_len,
106                    const char *label, size_t label_len,
107                    const uint8_t *seed1, size_t seed1_len,
108                    const uint8_t *seed2, size_t seed2_len) {
109  if (out_len == 0) {
110    return 1;
111  }
112
113  OPENSSL_memset(out, 0, out_len);
114
115  const EVP_MD *const original_digest = digest;
116  FIPS_service_indicator_lock_state();
117  int ret = 0;
118
119  if (digest == EVP_md5_sha1()) {
120    // If using the MD5/SHA1 PRF, |secret| is partitioned between MD5 and SHA-1.
121    size_t secret_half = secret_len - (secret_len / 2);
122    if (!tls1_P_hash(out, out_len, EVP_md5(), secret, secret_half, label,
123                     label_len, seed1, seed1_len, seed2, seed2_len)) {
124      goto end;
125    }
126
127    // Note that, if |secret_len| is odd, the two halves share a byte.
128    secret += secret_len - secret_half;
129    secret_len = secret_half;
130    digest = EVP_sha1();
131  }
132
133  ret = tls1_P_hash(out, out_len, digest, secret, secret_len, label, label_len,
134                    seed1, seed1_len, seed2, seed2_len);
135
136end:
137  FIPS_service_indicator_unlock_state();
138  if (ret) {
139    TLSKDF_verify_service_indicator(original_digest);
140  }
141  return ret;
142}
143
144int CRYPTO_tls13_hkdf_expand_label(uint8_t *out, size_t out_len,
145                                   const EVP_MD *digest,  //
146                                   const uint8_t *secret, size_t secret_len,
147                                   const uint8_t *label, size_t label_len,
148                                   const uint8_t *hash, size_t hash_len) {
149  static const uint8_t kProtocolLabel[] = "tls13 ";
150  CBB cbb, child;
151  uint8_t *hkdf_label = NULL;
152  size_t hkdf_label_len;
153
154  FIPS_service_indicator_lock_state();
155  CBB_zero(&cbb);
156  if (!CBB_init(&cbb, 2 + 1 + sizeof(kProtocolLabel) - 1 + label_len + 1 +
157                          hash_len) ||
158      !CBB_add_u16(&cbb, out_len) ||
159      !CBB_add_u8_length_prefixed(&cbb, &child) ||
160      !CBB_add_bytes(&child, kProtocolLabel, sizeof(kProtocolLabel) - 1) ||
161      !CBB_add_bytes(&child, label, label_len) ||
162      !CBB_add_u8_length_prefixed(&cbb, &child) ||
163      !CBB_add_bytes(&child, hash, hash_len) ||
164      !CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) {
165    CBB_cleanup(&cbb);
166    FIPS_service_indicator_unlock_state();
167    return 0;
168  }
169
170  const int ret = HKDF_expand(out, out_len, digest, secret, secret_len,
171                              hkdf_label, hkdf_label_len);
172  OPENSSL_free(hkdf_label);
173
174  FIPS_service_indicator_unlock_state();
175  if (ret) {
176    TLSKDF_verify_service_indicator(digest);
177  }
178  return ret;
179}
180
181